TECTONIC DEVELOPMENT OF THE PIONEER STRUCTURAL COMPLEX, PIONEER MOUNTAINS, CENTRAL IDAHO (CORE, DETACHMENT, EXTENSION).

Persistent Link:
http://hdl.handle.net/10150/183813
Title:
TECTONIC DEVELOPMENT OF THE PIONEER STRUCTURAL COMPLEX, PIONEER MOUNTAINS, CENTRAL IDAHO (CORE, DETACHMENT, EXTENSION).
Author:
WUST, STEPHEN LOUIS.
Issue Date:
1986
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The Pioneer Mountains of Idaho expose a lower plate core of Precambrian and Ordovician metasedimentary rocks, which are intruded by Cretaceous and Eocene plutonic bodies. The core is separated by a detachment fault from a surrounding upper plate of Paleozoic and Tertiary sedimentary and volcanic units. The detachment system developed during a Tertiary extensional event which overprinted Paleozoic and Mesozoic east-directed compressional features, and exhibits both brittle and ductile (mylonitic) deformation. Stretching lineations in the mylonite and striations along the detachment surface both cluster around N65W. Composite planar fabrics (s- and c-surfaces) in the mylonite and limited development of a mylonitic front along the NW side of the core both suggest a top-to-the-west sense of shear. Minimum translation is estimated at about 17 km. The Pioneer structural complex is one of a number of metamorphic core complexes present along the North American Cordillera. All exhibit Tertiary extensional deformation, expressed as detachment faults structurally adjacent to ductile mylonitic shear zones. Extension directions, as indicated by stretching lineations within mylonite and striations along detachment faults, fall into regional groups in which the directions are similar in trend throughout each group. Asymmetric fabrics on both small and large scales give senses of shear and indicate that tectonic vergence within each group is directed outward from a central axis. The regional consistency of extension directions implies a regional control of extension in metamorphic core complexes. Much of central Idaho, and possibly a large part of eastern Idaho as well, may be riding on the upper part of an extensive detachment terrane, of which the Pioneer complex exposes the deeper levels. The Pioneer complex, and other core complexes, owes its present elevation to isostatic uplift over an overthickened crustal welt of local scale. Larger-scale uplift may be due to a similar isostatic adjustment over a broad zone of crustal thickening from Mesozoic compressional tectonics and intrusion.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Plate tectonics -- Idaho -- Pioneer Mountains.; Geology, Structural.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Dickinson, Bill

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleTECTONIC DEVELOPMENT OF THE PIONEER STRUCTURAL COMPLEX, PIONEER MOUNTAINS, CENTRAL IDAHO (CORE, DETACHMENT, EXTENSION).en_US
dc.creatorWUST, STEPHEN LOUIS.en_US
dc.contributor.authorWUST, STEPHEN LOUIS.en_US
dc.date.issued1986en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe Pioneer Mountains of Idaho expose a lower plate core of Precambrian and Ordovician metasedimentary rocks, which are intruded by Cretaceous and Eocene plutonic bodies. The core is separated by a detachment fault from a surrounding upper plate of Paleozoic and Tertiary sedimentary and volcanic units. The detachment system developed during a Tertiary extensional event which overprinted Paleozoic and Mesozoic east-directed compressional features, and exhibits both brittle and ductile (mylonitic) deformation. Stretching lineations in the mylonite and striations along the detachment surface both cluster around N65W. Composite planar fabrics (s- and c-surfaces) in the mylonite and limited development of a mylonitic front along the NW side of the core both suggest a top-to-the-west sense of shear. Minimum translation is estimated at about 17 km. The Pioneer structural complex is one of a number of metamorphic core complexes present along the North American Cordillera. All exhibit Tertiary extensional deformation, expressed as detachment faults structurally adjacent to ductile mylonitic shear zones. Extension directions, as indicated by stretching lineations within mylonite and striations along detachment faults, fall into regional groups in which the directions are similar in trend throughout each group. Asymmetric fabrics on both small and large scales give senses of shear and indicate that tectonic vergence within each group is directed outward from a central axis. The regional consistency of extension directions implies a regional control of extension in metamorphic core complexes. Much of central Idaho, and possibly a large part of eastern Idaho as well, may be riding on the upper part of an extensive detachment terrane, of which the Pioneer complex exposes the deeper levels. The Pioneer complex, and other core complexes, owes its present elevation to isostatic uplift over an overthickened crustal welt of local scale. Larger-scale uplift may be due to a similar isostatic adjustment over a broad zone of crustal thickening from Mesozoic compressional tectonics and intrusion.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPlate tectonics -- Idaho -- Pioneer Mountains.en_US
dc.subjectGeology, Structural.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDickinson, Billen_US
dc.contributor.committeememberConey, Peteren_US
dc.contributor.committeememberDavis, Georgeen_US
dc.contributor.committeememberChase, Clemen_US
dc.contributor.committeememberButler, Boben_US
dc.identifier.proquest8613842en_US
dc.identifier.oclc697532342en_US
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